All I need is you
by charmed67
Summary: The family is out for the day, Magnus is working and Alec and Isabelle are home alone !
1. Chapter 1

Isabelle hated watching her brother with Magnus. Not because she didn't like Magnus, they were practically best friends. No it was because Magnus had Alec. And she didn't. 

She wanted him for herself! It was fine when he wasn't with anyone. But now she wanted Alec to hold her like he had when they were younger and she had nightmares. She wanted to be close to him, grasp his scent. Feel the worn out cotton of his sweater against her face. Run a hand through his hair, down his face and across his chest. She wondered if Alec remembered Isabelle kissing him when they were younger … Beacause she certainly did. 

. 

The institute was completely empty when Alec got up. 

It was in the high the thirties and he had woken up in a disgusting sweat. Everyone was probably out enjoying the nice weather. So he had had an icy shower that was absolute heaven. Wrapping his waist in a towel, he walked out in only that. He was the only one home after all. Walking into the kitchen for some breakfast he was in for a surprise. 

Isabelle was bent down looking for something in the fridge. She was wearing nothing but a skimpy turquoise bikini, her entire body shiny from baby oil. Her ink black hair in loose waves. 

"I really wish we had a regular fridge with the freezer on top, it's such a pain on the bottom." said Isabelle sucking on a popsicle. 

" It's just a fridge Izzy." Alec couldn't help looking at his sister. He had always sort of thought of her differently.. But she was her sister, so he didn't. It wasn't right. And he had Magnus, who he was very much in love with.

"Your being awefully risky today, usually your fully dressed when you come out in the morning." Isabelle stretched her arms backward, pushing her chest out. Sometimes Alec wondered if she did these things on purpose. 

"I thought I was the only one home."

"Were the only ones home, mom and dad are out.." The way Isabelle was suggestivly looking at him, made him think. Did she feel sort of the same way? No no they were brother and sister, that was utter nonsense.

Was it?

"I don't think they'll be back for a while and Jace and Clary went to the beach. Just you and me today." God could he take a hint thought Isabelle?

"Well do you wanna hang out today? Magnus has to work."

"Sure, want to go for a dip?"

And the next thing Alec knew he was in the underground pool in the backyard of the institute. Stupid Clary and Jace why would they bother with a beach when their was a backyard pool? They really should've stayed, shouldn't have left Alec and Isabelle alone. Not today. Alec just had a bad feeling.

"Geez Alec in your own world much" said Isabelle chuckling. She was floating around him drinking vodka straight. "I know im not as interesting as Magnus but you could still pay me some attenchion." Isabelle said it jokingly but she truly meant it. 

"Can I have a drink?" She handed him the vodka.. Don't worry Izzy you really are, even if you don't have a pound of glitter on your face or spiked up hair.

Alec leaned on her floaty. He went to pass her the bottle accidently grazing her chest. 

"Sorry" said Alec blushing. 

She said nothing. She just stared at him curiously. Moving in a little closer she tilted. Alec moved a bit closer, not sure what was happening exactly. 

And then she moved all the way in, her lips crushing against his. She tasted so sweet. To Isabelle, Alec tasted minty. And then he broke away.

"Sorry" he repeated. 

"No don't be, I'm not… She hopped off her floaty and swam to the stairs. Turning back her head she asked if he was coming. 

A little while later is Alec's room…

Their clothes, well Isabelle's bikini and Alec's shorts, led a trail to his bed. They were making out fiercely, among other things. This was soo wrong. But it just felt soo good. Being with Isabelle was different than being with Magnus. Not nessasarilly better but definatly different. Oh Magnus, he could never find out. No one could ever find out. 

And then the light flipped on.

"What the hell is going on here?" said Maryse Lightwood, their mother.

Please review and tell me if you liked it and if I should go on !!! Thank you!!!


	2. Chapter 2

**A week or so later …**

**The dinner party Maryse had planned was turning out perfectly. Everyone had showed up with extra guests. The caterers were serving the wrong food and decorations were falling down, all of them. It may have been hell for Maryse but it was secretly anticipated by Alec and Isabelle. It kept her busy.**

**Isabelle shrugged off their mothers yells and lectures on how very, very wrong it was. Alec cringed at the thought of it. Yet he still didn't deny being felt up at breakfast. The only time Maryse wasn't watching them like a hawk, she claimed she needed her beauty sleep.**

**Isabelle suspected Clary knew something.. Maybe she was let in on the little secret? Perhaps caught on to why Alec had said the eggs were just so damn good that one day? Not like she could say anything, filthy hippicrate.**

"**Where's Magnus" asked Clary. **

"**Oh he'll be here later, work stuff" Alec mumbled. He hoped Clary hadn't caught on to Alec staring at Isabelle… Well it was hard not too! She was wearing an extremely low cut purple dress that just clung to her. He wanted to tell her to put some clothes on, no one else should be seeing that.**

"**Yeah I would of thought he would have been here by now, this seems like his kind of thing." said Jace , his hair was slightly ruffled and he was extremely happy looking. Well he and Clary had just gone to 'move some furniture'. Sneaky bastards. Hmm that gave Alec an idea…**

"**Oh it is, I believe he even bought a new suit." said Alec. "Excuse me I'm going to get a drink." Alec looked at Isabelle again, and this time she was looking back. He gave a little nod to the kitchen, she smirked. **

"**Oh but there's waiters all around us" said Clary trying to sound casual. Like she hadn't just seen what Alec did.**

"**I think I need something a bit stronger."**

**Jace raised his eyebrows and shook his head. Clary was sort of turning Jace into a pansy. **

**Alec got there before Isabelle. He poured himself a shot his dads expensive scotch.. After drinking the burning liquer, he realized he need more than that. **

"**May I have a sip" asked Isabelle from behind him. She gave him a little smile. And before he could hand it over, Isabelle was crushing her lips against his. **

**Her mouth was hot and she tasted of cherry's. She unbuttoned his shirt, running her hands all over his exposed chest. Her hand moved down to his belt.**

**Alec unzipped Isabelle's dress and lifted her up on the counter, slipping the dress straps off. He bit her lip a little, and then trailed kisses down her neck and to her breasts.**

**Isabelle unbuckled his belt and unzipped his pants, pulling them down a little. Daring him to further .. Alec ran his hands up Isabelle's thighs, reaching to pull off her lacy black thong. **

" **Magnus is here!" someone yelled excitedly. **

_**hmm not really sure where I'm going with this … Any ideas ? PLEASE REVIEW **__**J**_


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